The invention relates to polymer-bound writing substances for writing, drawing and/or painting tools.
Such writing substances for writing, drawing and/or painting are known in principle. “Polymer-bound graphite-based writing substances for writing, drawing and/or painting” are understood to be writing substances which are inserted rigidly into wood or other materials which can be sharpened, and also writing substances which are held displaceably in a rigid casing. Examples of this include wood-cased pencils and writing substances for mechanical pencils, for example ‘retractable pencils’. In this case the writing substances normally have an outer diameter in the range of approximately 0.3 mm to 6 mm.
For example, polymer-bound graphite writing substances are known from DE 38 27 968 C1. Such raw writing substances contain a polymer bonding agent, lubricants and fillers.
A drawback in the production of such writing substances is that although the writing and painting properties thereof are very good with a high filler material content of more than 50 wt. %, the viscosity of the writing substance mass during extrusion is very high and the extrusion pressure thus required in the die and in the extruder reaches very high values. The head pressure is approximately 350 bar. This is disadvantageous since a greater dimensioning of the extruder and complex configuration are required. The service life of the equipment and dies is much reduced by the high extrusion pressure.